This invention relates generally to a plier tool for applying a locked gripping force on a workpiece positioned between the opposed jaws of the tool. More particularly, this invention pertains to a locking plier tool capable of gripping and locking onto a workpiece and maintaining its gripping force on the workpiece until intentionally manually released. The tool is manually operated by one hand of the operator and manually adjustable by the same hand to change the clamping pressure exerted by the tool.
The prior art has provided a number of different types of adjustable locking pliers or wrenches where the pressure exerted by the jaws on the workpiece is selectively adjustable. Adjustment is usually accomplished by manually rotating a threaded shaft. Typically, it is necessary for the operator to hold the tool in one hand while using his other hand to manipulate the adjusting mechanism and then test the gripping action of the tool on the workpiece to determine if the desired pressure intensity or gripping force has been reached.
There remains a definite need for a locking plier tool capable of one-handed operation wherein the jaws of the tool can be clamped onto a workpiece and locked in position while the operator's other hand remains free, and being adjustable as to the jaw pressure exerted on the workpiece by the same hand holding the tool, and then being capable of release from the workpiece while the operator's other hand still remains free.
Typical of a locking plier tool in the prior art which provides means for varying the gripping pressure between opposed jaws is the tool disclosed in U.S. Pat. No. 3,600,986. This tool enables variance of the tool's jaw pressure by rotation of a threaded shaft and purports to provide a quick release lever. The tool, however, is incapable of being adjusted by the same hand used to close the handles and can only be released from the workpiece as a two-handed operation.